This invention relates to a process for preparing an iron-manganese colorant, from an aqueous media containing metal ions, having an effective amount of iron and manganese present to impart color to building materials such as bricks, ceramic tiles, paving shapes, concrete block and other functional building units.
Large amounts of metal chlorides arise as by-products from various industrial processes. For example, in a chloride process for making TiO.sub.2, titanium bearing material or ore is chlorinated to produce TiCl.sub.4 and other metal chloride by-products. The metal chloride by-products are highly acidic and often contain iron chlorides as a major ingredient as well as manganese chloride. Many processes to treat these materials are expensive and produce a product that must still be disposed of by neutralization, landfilling, deepwelling or other disposal methods.
The need therefore exists for a process for treating aqueous media containing metal ions that produces saleable products.
Iron oxides or iron hydroxides are used in ceramic products for the building industry as red, black, brown or yellow pigments and manganese oxides as brown-black pigments. A combination of iron and manganese oxides can be used to impart dark red to brown or even black colors to ceramic materials including bricks. For example, U.S. Pat. No. 3,276,894 discloses oxidation of iron with aromatic nitro compounds in the presence of Fe(II) salt solutions and/or suspensions of hydrolyzable salts, oxides or hydroxides and further in the presence of manganese compounds or metal. Therein, an expensive, high temperature calcination step is required to form a metal oxide pigment. Further, there is neither disclosure therein of metal hydroxide pigments nor metal carbonate pigments.